The present invention relates generally to wastewater treatment, and in particular, to the treatment and treatment of marine wastewater onboard small marine vessels.
The one or more embodiments of the invention comprise methods, apparatus and systems for the treatment of marine wastewater, wherein the systems or apparatus are installed on marine vessels. One or more embodiments include passing a pre-determined volume of wastewater or sewage generated onboard the vessel into a wastewater treatment apparatus. The wastewater treatment apparatus comprises a mixing spool, an electrolytic cell, one or more oxidation chambers and one or more dehalogenation chambers. A seawater-rich environment is maintained within the wastewater treatment apparatus by routing and mixing a pre-determined volume of seawater with the wastewater to be treated. The ratio of the seawater to the wastewater in the mixture is controlled, and may be at least 20:1. The seawater may be routed to the wastewater treatment apparatus at a rate of between 60-120 liters per minute and the wastewater may be routed to the wastewater treatment apparatus at a rate of between 1-6 liters per minute.
The wastewater and seawater mixture or solution may be then routed through the electrolytic cell where DC current and voltage are applied to the mixture. Sodium hypochlorite and mixed oxidants may be generated from the salt-laden seawater which may be used to effectively oxidize the wastewater. Significant changes to the wastewater may also take place due to the electrical field produced by the application of the electrical current and voltage and a rapid oxidation of the bacteria by the sodium hypochlorite and mixed oxidants.
Upon exiting the electrolytic cell, the mixture is further oxidized within the oxidation chamber, until the mixture is substantially fully oxidized by the hypochlorite and mixed oxidants. In one embodiment, each of the one or more oxidation chambers may further comprise one or more cylindrical oxidizer tubes. Proper turbulence may be maintained in the oxidizer tubes by adjusting their size and number. This adjustment may be further dependent on the volume of wastewater to be treated.
The substantially fully oxidized mixture is then treated with a pre-measured quantity of a reducing agent, followed by subjecting the mixture to a serpentine flow path within the one or more dehalogenation chambers. The serpentine flow path may ensure that the reducing agent is contacted with the mixture for an optimal time, preferably between 5 seconds to 30 seconds, to completely neutralize any remaining residual oxidants. Each of the one or more dehalogenation chambers may also comprise one or more cylindrical dehalogenation tubes.
A seacheck valve may be used to route the treated effluent overboard the vessel. A flow monitor may be incorporated into the process to ensure proper volumetric flow control. The flow meter may also ensure that optimal utilization of the reducing agent and sodium hypochlorite and mixed oxidants is maintained.
The International Maritime Organization (the “IMO”) is a specialized agency of the United Nations and it is mainly tasked with the development and maintenance of a comprehensive regulatory framework for shipping. This includes safety and environmental concerns related to the maritime industry. IMO Resolution MEPC.159(55) provides guidelines on treated effluent standards. The one or more embodiments of the invention may meet or exceed the requirements for treated effluent under MEPC.159(55). The discharged effluent may comprise less than 25 mg/L Biological Oxygen Demand (BOD5), less than 125 mg/L Chemical Oxygen Demand (COD), less than 100 cfu/100 ml coliform, less than 35 mg/L Total Suspended Solids (TSS), less than 0.5 mg/L total oxidants and pH between 6-8.5 in full compliance with MEPC.159(55).